1. Technical Field
This invention relates to a magnetic recording medium, more particularly, to a magnetic recording medium for use in magnetic read/write equipment such as magnetic disk equipment known as hard disk drives (HDD), and further particularly, to the structure of a magnetic recording medium having a high recording density.
2. Background Art
High-capacity storage devices, especially hard disk drives featuring a high data transfer rate, quick access, high reliability and low price have marked a significant advance toward higher capacity and higher density. An improvement in areal recording density is accomplished by miniaturizing recording magnetic domains formed in the magnetic recording layer. At present, the density has exceeded 5 gigabits per square inch, with development efforts being made with the target on 10 gigabits to 100 gigabits.
Used as the magnetic head for write and read operation is a combined magnetic head in which an inductive head as the write head is combined with a magnetoresistive head (MR head) as the read head. Since the output of the MR head is determined by a magnetic flux change per circumferential unit length, in principle, the output does not decline even when the track width is minimized. The use of the MR head thus suggests a possibility to realize narrow tracks. The same applies to a giant magnetoresistive head (GMR head) with which a higher recording density is expected.
However, if the track width is too narrow, the interference or crosstalk between magnetic signals from adjacent recording tracks increases so that the degradation of read signals becomes a problem.
The areal recording density can also be increased by reducing the recording bit length. If the recording bit length is too short, the interference or partial erasure between magnetic signals from adjacent bits increases so that the degradation of read signals becomes a problem.
JP-A 9-297918 discloses a magnetic recording medium in which a plurality of recording portions are provided in the form of rectangular regions having two side lengths equal to a track width and a minimum bit-determining length, the plurality of recording portions are separated by space areas, and information is stored in the recording portions. This medium is a so-called patterned medium. The patterned medium is effective for suppressing the degradation of read signals by crosstalk and partial erasure.
For the achievement of a high recording density, it is also requisite to reduce the flying height of a slider having a magnetic head mounted thereon. However, reducing the flying height of a slider increases the frequency at which the slider comes in contact with the magnetic recording medium by disturbances. In the event of slider rubbing, the magnetic recording layer can be flawed whereby the recorded information is disrupted. For the patterned medium, however, effective means for avoiding the disruption of recorded information by the contact of the medium with the slider has not heretofore been proposed.
In conjunction with a so-called patterned medium comprising recording tracks each having an array of unit minute recording portions of a magnetic material separated by non-recording portions of a nonmagnetic material, an object of the invention is to prevent the recorded information from being disrupted by contact of a magnetic head slider with the medium.
This and other objects are attained by the present invention which is defined below.
(1) A magnetic recording medium comprising recording tracks each having an array of unit minute recording portions of a magnetic material separated by non-recording portions of a nonmagnetic material, the unit minute recording portions having a lower surface height than the non-recording portions.
(2) The magnetic recording medium of (1) wherein the surface height of the unit minute recording portions is 5 to 30 nm lower than the surface height of the non-recording portions.
(3) The magnetic recording medium of (1) wherein each unit minute recording portion is a single magnetic domain.
(4) The magnetic recording medium of (1) wherein the unit minute recording portions are constructed of any one of Co, Coxe2x80x94Cr, Coxe2x80x94Crxe2x80x94Ta and Coxe2x80x94Crxe2x80x94Pt.
In the magnetic recording medium of the invention, the surface height of the unit minute recording portions is set lower than the surface height of the non-recording portions. Even when the slider rubs the surface of the medium during magnetic write/read operation, the slider does not contact the unit minute recording portions. Accordingly, the recorded information is not disrupted even if the flying height of the slider is reduced in order to improve the recording density.
One means employed in the prior art for preventing a slider from being stuck to the surface of a medium is to form a magnetic recording layer on a locally raised and depressed surface of a substrate so that the medium surface may become locally raised and depressed. By contrast, the medium of the invention eliminates a need for a special structure for preventing sticking because the unit minute recording portions and non-recording portions of different surface heights form depressions and protrusions.